The influence of ovarian activity and uterine involution determined by ultrasonography on subsequent reproductive performance of dairy cows

The objective of this study was to test the hypothesis that a follicle >8 m m diameter in the ovary ipsilateral to the previously gravid uterine horn ( PGUH), between 14 and 28 days postpartum, improves subsequent reproductive performance. Lactating Holstein-Friesian cows (n = 284) in 3 commercial her ds were examined using transrectal ultrasonography once between 14 and 28 d ays postpartum to determine associations between uterine and ovarian measur ements and subsequent fertility. There were fewer cows with a corpus luteum in the ovary ipsilateral to the PGUH compared with the contralateral ovary (16.9% vs. 37.0%; P < 0.001). In addition, in the ovary ipsilateral to the PGUH there were fewer follicles >5 mm diameter (mean +/- SEM; 0.69 +/- 0.0 6 vs. 1.02 +/- 0.06; P < 0.001) and fewer animals with a follicle >8 mm dia meter (26.1% vs. 49.6%; P < 0.001). These differences between the ovaries i psilateral or contralateral to the PGUH declined with increasing time betwe en 14 and 28 days postpartum. The presence of a purulent vaginal discharge decreased the number of animals with a corpus luteum in the ovary contralat eral to the PGUH (45/143 vs. 60/141; P < 0.05), but not in the ovary ipsila teral to the PGUH. The presence of a follicle >8 mm diameter in the ovary i psilateral to the PGUH was associated with a shorter calving to conception interval compared with animals without such a follicle (99.0 +/- 5.6 days, n = 74, vs. 112.8 +/- 4.4 days, n = 210; P < 0.05). These observations rais e an intriguing issue: how does this follicle affect subsequent fertility - does the follicle exert a local influence on the uterus, or vice versa? (C ) 2000 by Elsevier Science Inc.